Liquid crystal display and manufacturing method of the same

ABSTRACT

A liquid crystal display includes a plurality of gate lines (GØ-Gn), a plurality of data lines (D 1 -Dn) formed in a direction crossing the gate lines, a plurality of pixel electrodes formed in a pixel area defined by the gate lines and the data lines, the pixel electrodes indicating pictures by a control of the corresponding gate lines, and a light volume adjusting layer formed on a lower layer of the pixel electrodes controlled by a second one of the gate lines (G 1 ). A method for manufacturing a liquid crystal display includes the steps of: forming gate lines and a gate electrode on a substrate, forming a gate insulating film on the board including the gate electrode, forming a first active layer on the gate insulating film corresponding to an upper portion of the gate electrode and forming a second active layer on the gate insulating film corresponding to a portion where pixel electrodes are formed, forming source/drain electrodes on an upper portion of the first active layer, and forming a passivation film on the whole surface of the active layer including the source/drain electrodes.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application claims benefit of Korean Patent Application No.P2000-81174, filed on Dec. 23, 2000, the entirety of which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a display device, and moreparticularly, to a liquid crystal display and a manufacturing method ofthe same.

[0004] 2. Description of the Related Art

[0005] There are various pixel design methods for a TFT-LCD (Thin FilmTransistor-Liquid Crystal Display). A designer must select between anamorphous-silicon TFT (a-Si:H TFT) and a Polycrystalline silicon TFT,and then, must select either a Back Channel Etched (BCE) TFT structure,a Channel Passivated (CHP) TFT structure and other TFT structures. Afterthat, the designer must map out a TFT arrangement plan and a design of apixel electrode and determine a storage capacitance (hereinafter, calledCst) type.

[0006] The Cst type is classified into a storage-on-common method and astorage-on-gate method according to methods for manufacturing a commonelectrode. In the storage-on-common method, the common electrode of theCst is made separately, but in the storage-on-gate method, a portion ofa gate wiring of a front end is used as the common electrode of the Cst.Compared with the storage on common method, the TFT-LCD of thestorage-on-gate method, which does not have the separate wiring for theCst, has a larger aperture ratio and there is no overlapped portionbetween data lines and the Cst wiring, and thereby opens in the datalines are reduced and the recovery rate is increased. However, becausethe Cst which is formed on the gate wiring makes a signal delay of thegate line, the gate wiring must be made of low resistance metal, such asaluminum (Al) or aluminum alloy (Al alloy). Moreover, based on anelectric charge of a pixel, because it is not a perfect dot inversion orcolumn inversion, picture quality is relatively lowered.

[0007] Hereinafter, referring to the drawings, a conventional liquidcrystal display will be described in detail.

[0008]FIG. 1 is a plan view showing a unit pixel area of a TFT-LCD ofthe storage on gate type.

[0009] As shown in FIG. 1, two data lines 11 are aligned parallel toeach other, and two scanning lines or gate lines 12 are aligned parallelto each other in a perpendicular direction to the data lines.Furthermore, TFTs, including source/drain electrodes 13 and 14 and agate line 15, is formed at intersections of the data lines 11 and thegate lines 12. At the center portion of the pixel area is formed a pixelelectrode 16 electrically connected with the drain electrode 14. A Cst17 is formed on an upper end of the pixel area using a portion of thegate wiring as an electrode. The Cst 17 helps to charge a signalvoltage.

[0010]FIG. 2 is a plan view of the conventional liquid crystal display.

[0011] In general, liquid crystal display panel includes a plurality ofscanning lines or gate lines 21 (GØ-Gn) aligned in one direction and inregular intervals, a plurality of data lines 22 (D1-Dn) aligned in aperpendicular direction to the gate lines and in regular intervals, aplurality of pixel electrodes (not shown) defined by the gate lines andthe data lines, and a plurality of switching devices such as TFTs (notshown) switched by signals of the gate lines and applying data signalssupplied through the data lines to the pixel electrodes.

[0012] Furthermore, driver ICs 23 and 24 for supplying gate drivingsignals and data signals are attached to a portion of the gate lines andthe data lines. That is, a pad is formed at ends of the gate lines andthe data lines, where the driving drive ICs will be connected.

[0013]FIG. 3 is a sectional view along line I-I′ of FIG. 2.

[0014] First, in a TFT substrate, which is a lower substrate, a gateinsulating film 32 is piled up on an insulating substrate 31. First andsecond data lines 33 and 34 are patterned on the gate insulating film32. A passivation layer 35 of insulated material, is formed on thesubstrate including the data lines. Moreover, a pixel electrode 36 ispatterned on the passivation layer 35 corresponding between the firstand second data lines 33 and 34. A color filter substrate, which is anupper substrate, includes black matrixes 38 formed in regular intervalsand a color filter layer 39 formed in a space between the black matrixes38.

[0015] However, the conventional liquid crystal display and themanufacturing methods thereof have the following problems.

[0016] The final voltage applied to a pixel is fixed after a couplingphenomenon acts on it by the gate signal. That is, the differencebetween V_(gh) and V_(gl) is the size of a voltage applied to pixel.However, in the case of the number Ø gate line (the first gate line, GØ)(see FIG. 2), because only the V_(gl) signal of the V_(gh) and V_(gl)signals, is applied there occurs a difference between the voltageapplied to those pixels and the voltage applied to the pixels of anothergate line, and thereby a light phenomenon occurs to pixels controlled bythe number 1 gate line (G1).

[0017] Generally, as a counter measure of such a light phenomenon, thereis a method to apply the same signal as a prescribed gate line to thenumber Ø gate line (GØ), but this requires an additional material cost.

SUMMARY OF THE INVENTION

[0018] It is, therefore, an object of the present invention to provide aliquid crystal device capable of blocking a transmission of light andmaintaining a luminosity of a liquid crystal display panel uniformly byforming an active layer of amorphous silicone (a-Sh:H) material on alower layer of pixels controlled by a number 1 scanning line or gateline (G1).

[0019] To achieve the above object, the present invention provides aliquid crystal display including: a plurality of scanning lines or gatelines (GØ-Gn) formed in a first direction; a plurality of data lines(D1-Dn) formed in a direction crossing the gate lines; a plurality ofpixel electrodes formed in a pixel area defined by the gate lines andthe data lines, the pixel electrodes indicating pictures by a control ofthe corresponding gate lines; and a light volume adjusting layer formedon a lower layer of the pixel electrodes controlled by a second gateline.

[0020] In another aspect, to achieve the above object, the presentinvention provides a method for manufacturing a liquid crystal display,the method including the steps of: forming gate lines and a gateelectrode on an insulating board; forming a gate insulating film on theboard including the gate electrode; forming a first active layer on thegate insulating film corresponding to an upper portion of the gateelectrode and forming a second active layer on the gate insulating filmcorresponding to a portion where pixel electrodes are formed; formingsource/drain electrodes on an upper portion of the first active layer;and forming a passivation film on the whole surface of the active layerincluding the source/drain electrodes.

[0021] Flicker, which is a twinkle phenomenon of panel picture, occurswhen there is a difference between (+) and (−) voltages of data lines tovoltage applied to a common electrode. To relieve a level of theflicker, a TFT-LCD structure may be changed and the difference between(+) and (−) voltages of the data lines may be compensated by enlarging aCst volume. However, in the TFT-LCD structure of a storage on gatemethod, if the Cst volume is enlarged, there may occur unfavorable sideeffects on the number Ø gate line, to which only the V_(gl) signal, ofV_(gh) and V_(gl) signals, is applied, since the Cst is a portion of thegate line. For an example, the line light phenomenon occurs to pixelelectrodes controlled by the number 1 gate line (GI).

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further objects and advantages of the invention can be more fullyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

[0023]FIG. 1 is a plan view showing a unit pixel area of a conventionalTFT-LCD of a storage on gate method;

[0024]FIG. 2 is a plan view of a conventional liquid crystal display;

[0025]FIG. 3 is a sectional view of the liquid crystal display along theline of I-I′ of FIG. 2;

[0026]FIG. 4 is a sectional view of a liquid crystal display accordingto the present invention; and

[0027]FIGS. 5a through 5 d are sectional views for explaining amanufacturing method of the liquid crystal display according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] The present invention will now be described in detail inconnection with preferred embodiments with reference to the accompanyingdrawings. For reference, like reference characters designatecorresponding parts throughout several views.

[0029] In the liquid crystal display described with respect to FIG. 4,an active layer of, e.g., amorphous silicon (a-Sh:H) material, on alower layer of pixels controlled by the number one scanning line or gateline (G1) (see FIG. 2) serves to restrict a transmission of light topixel electrodes and to restrict the line light phenomenon.

[0030] Hereinafter, referring to the drawings, the liquid crystaldisplay and its manufacturing method according to the present inventionare described in detail.

[0031]FIG. 4 is a sectional view of the liquid crystal display accordingto the present invention and shows unit pixels of a plurality of pixelareas controlled by the number 1 gate line (G1).

[0032] An upper substrate, on which a color filter layer is formed, isthe same as the related arts, and therefore, only a structure of a lowersubstrate, on which a TFT (Thin Film Transistor) is formed, will bedescribed.

[0033] A gate insulating film 52 is formed on a substrate 51, a firstactive layer, which is a channel layer of the TFT, (not shown) is formedon the gate insulating film 52, and a second active layer 53 is formedon the gate insulating film corresponding to a portion where the pixelelectrodes are formed. Here, the first and second active layers arepreferably made of amorphous silicon (a-Sh:H) material. First and seconddata lines 54 and 55 are patterned at right and left portions of thesecond active layer 53, and a passivation layer 56 of insulating filmmaterial is formed on the substrate 51 including the data lines. Aplurality of pixel electrodes 57 are patterned on the passivation layer56 corresponding to the active layer 53.

[0034] The second active layer 53 can change the thickness according toa transmission of light. When the active layer is patterned, thethickness of the second active layer 53 can be changed by adjusting anetching speed during an etching process after a photolithographyprocess. Moreover, also an area of the active layer can be adjustedusing the photolithography process.

[0035]FIGS. 5a through 5 d are sectional views for explaining amanufacturing method of the liquid crystal display according to thepresent invention. The upper substrate, on which the color filter isformed, is the same as the related art, and therefore, only the lowersubstrate will be described.

[0036] As shown in FIG. 5a, the gate insulating film 52 is formed byevaporating an insulating material of silicon nitride (SiN_(x)) on thesubstrate 51 using a PECVD (Plasma Enhanced Chemical Vapor Deposition)method.

[0037] As shown in FIG. 5b, the active layer 53 of the amorphous silicon(a-Sh:H) material is evaporated on the gate insulating film 52 using thePECVD method, and then patterned through a photolithography process, anetching process and a strip process. Beneficially, the active layer 53is the same as the amorphous silicon layer, which is a channel layer ofthe TFT, and thereby the active layer is formed when the channel layerof the TFT is formed, without any additional process.

[0038] As shown in FIG. 5c, conductive metals disposed at both sides ofthe active layer 53 are evaporated using a sputtering method, and then,patterned to form data lines 54 and 55.

[0039] As shown in FIG. 5d, the passivation layer 56 of insulatingmaterial is formed on the whole surface of the substrate 51 includingthe active layer 53 and the data lines 54 and 55. A transparentconductive film of, e.g., Indium Tin Oxide (ITO) material, is evaporatedon the passivation layer 56 corresponding to the active layer using thesputtering method, and then, patterned to form the pixel electrodes 57.

[0040] After that, it is not shown in the drawings, but if the substrate51, on which the pixel electrode is formed, and the substrate, on whichthe color filter is formed, are cohered and liquid crystal is sealed,the manufacturing process of the liquid crystal display according to thepresent invention is finished.

[0041] As described above, the liquid crystal display and itsmanufacturing method according to the present invention have thefollowing effects.

[0042] When the pixel electrode controlled by the number 1 gate line(G1) is formed, the active layer is formed on a lower layer of the pixelelectrode to restrict the transmission of light, thereby preventing thelight phenomenon of the number 1 gate line (G1) due to the number Ø gateline (GØ) (see FIG. 2), to which only V_(gl) signal, of the V_(gh) andV_(gl) signals, is applied.

[0043] Furthermore, when the channel layer of the TFT is formed, theactive layer is formed without requiring additional process, therebychanging the thickness and the area of the active layer through theexisting process.

[0044] While the present invention has been described with reference tothe particular illustrative embodiments, it is not to be restricted bythe embodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

What is claimed is:
 1. A liquid crystal display comprising: a pluralityof gate lines (GØ-Gn) formed along a first direction; a plurality ofdata lines (D1-Dn) formed along a second direction substantiallyperpendicular to the first direction and crossing the gate lines; aplurality of pixel electrodes each formed in a pixel area defined by thegate lines and the data lines, the pixel electrodes indicating picturesunder control of the corresponding gate lines; and a light volumeadjusting layer formed on a lower layer of the pixel electrodescontrolled by a second gate line (G1) among the gate lines.
 2. Theliquid crystal display as claimed in claim 1, wherein the light volumeadjusting layer is an active layer.
 3. The liquid crystal display asclaimed in claim 2, wherein the active layer is an amorphous siliconlayer.
 4. A method for manufacturing a liquid crystal display, themethod comprising: forming gate lines and a gate electrode on asubstrate; forming a gate insulating film on the substrate, includingthe gate electrode; forming a first active layer on the gate insulatingfilm corresponding to an upper portion of the gate electrode and forminga second active layer on the gate insulating film corresponding to aportion where pixel electrodes are to be formed; forming source/drainelectrodes on an upper portion of the first active layer; and forming apassivation film on the whole surface of the active layer including thesource/drain electrodes.
 5. The method as claimed in claim 4, whereinthe first and second active layers are amorphous silicon layers.
 6. Themethod as claimed in claim 4, wherein a thickness of the second activelayer is changed according to the transmission of light.
 7. The methodas claimed in claim 6, wherein the second active layer is adjusted inarea according to an etching speed.
 8. A liquid crystal display (LCD)device, comprising: a substrate; a plurality of scanning lines (GØ-Gn)extending along a first direction on the substrate; a plurality of datalines (D1-Dn) extending along a second direction substantiallyperpendicular to the first direction on the substrate and crossing thescanning lines (GØ-Gn); a plurality of switching devices on thesubstrate arranged in a plurality of rows, each switching deviceconnected to one of the scanning lines (GØ-Gn) for controlling aswitching of the switching device and one of the data lines (D1-Dn) forapplying data to the switching device, wherein switching devices in eachrow are connected to a same scanning line, and wherein the rows ofswitching devices are sequentially scanned by the scanning lines(GØ-Gn); a plurality of pixel electrodes on the substrate in a pluralityof pixel areas defined by the scanning lines (GØ-Gn) and the data lines(D1-Dn), the pixel electrodes each being connected to a correspondingone of the switching devices; and a light transmission restricting layerformed on the substrate controlled by a second scanning line (G1) amongthe scanning lines (GØ-Gn).
 9. The LCD device of claim 8, wherein thelight transmission restricting layer is an active layer.
 10. The LCDdevice of claim 9, wherein the switching devices include a second activelayer.
 11. The LCD device of claim 9, wherein the active layer is anamorphous silicon layer.
 12. The LCD device of claim 8, furthercomprising an insulating material between the light transmissionrestricting layer and the substrate.
 13. A method for manufacturing aliquid crystal display, the method comprising: forming a plurality ofscanning lines (GØ-Gn) along a first direction on a substrate; formingan insulating layer on the substrate including the scanning lines(GØ-Gn); forming a light transmission restricting layer on theinsulating layer; forming a plurality of data lines (D1-Dn) along asecond direction substantially perpendicular to the first direction onthe substrate and crossing the scanning lines (GØ-Gn); and forming aplurality of pixel electrodes on the substrate in a plurality of pixelareas defined by the scanning lines (GØ-Gn) and the data lines (D1-Dn),the pixel electrodes each being controlled by one of the scanning lines,wherein the light transmission restricting layer is formed beneath pixelelectrodes controlled by a second scanning line (G1) among the scanninglines (GØ-Gn).
 14. The method of claim 13, further comprising forming asecond insulating layer on the light transmission restricting layerbefore forming the pixel electrodes.
 15. The method of claim 13, furthercomprising forming a plurality of switching devices on the substratearranged in a plurality of rows, each switching device connected to oneof the scanning lines (GØ-Gn) and one of the data lines (D1-Dn).
 16. Themethod of claim 13, wherein an active layer of the switching devices isformed while forming the light transmission restricting layer.